quick langton ant

fourmi.js

const parseGrid = ([str]) => str
    .split('\n')
    .map(row => row.trim())
    .filter(row => row.length > 0)
    .map(row => row.split('').map(char => char !== '.'))

const formatGrid = (rows, ant) => rows
    .map((row, y) => row.map((cell, x) => {
        if (ant.x === x && ant.y === y) {
            return '8'
        }
        return cell ? '#' : '.'
    }).join(''))
    .join('\n')


const calcNextGridState = (grid, ant) => {
    const antCell = grid[ant.y][ant.x];
    if (antCell) {
        // case blanche
        ant.dir = (ant.dir + 3) % 4
    } else {
        // case noire
        ant.dir = (ant.dir + 1) % 4
    }
    switch (ant.dir) {
        case directions.UP: ant.y -= 1; break;
        case directions.RIGHT: ant.x += 1; break;
        case directions.DOWN: ant.y += 1; break;
        case directions.LEFT: ant.x -= 1; break;
    }

    if (ant.y in grid && ant.x in grid[ant.y]) {
        grid[ant.y][ant.x] = !grid[ant.y][ant.x]
    }
}

const directions = {
    UP: 0,
    RIGHT: 1,
    DOWN: 2,
    LEFT: 3
};

(function loop(grid, ant, t = 1) {
    const out = formatGrid(grid, ant)
    console.log(`Turn ${t}\n${out}`)
    if (t < 100 && out.includes('#')) setTimeout(() => {
        calcNextGridState(grid, ant)
        loop(grid, ant, ++t)
    }, 300)
})(parseGrid`
....................
....................
....................
.....#..............
....................
....................
....................
....................
....................
....................
`, {
    x: 10,
    y: 5,
    dir: directions.UP
})